Home/CVE/Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField
CVE

CVE-2026-33433

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when headerField is configured with a non-canonical HTTP header name (e.g., x-auth-user instead of X-Auth-User), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries, the attacker-injected canonical one is read first, overriding Traefik's non-canonical write.

Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.

HIGH · CVSS 8.8 EPSS 0.00027
Act now
  • Public exploit or PoC is available
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-290Authentication Bypass by Spoofing
▤

Affected Products & Versions

3
traefik< 2.11.42
traefik>= 3.0.0 and < 3.6.12
traefikall versions
▤

Affected Packages

3
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
Go github.com/traefik/traefik
Go github.com/traefik/traefik/v2 MODERATE fixed in 2.11.42
Go github.com/traefik/traefik/v3 MODERATE fixed in 3.6.12
⚠

Public Exploits & PoCs

1
pocgithub.com · GHSA-qr99-7898-vr7cgithub.com
▣

Scoring & Timeline

8.8
HIGH · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD27 Mar 2026 · 03:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

1
rhsaRHSA-2026:10175Important
🔗

References & Sources

3
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/traefik/traefik/releases/tag/v2.11.42ProductRelease Notes
https://github.com/traefik/traefik/releases/tag/v3.6.11ProductRelease Notes
https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3ProductRelease Notes
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